JPH0356361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam generator used in a nuclear power plant, and more particularly to a vertical steam generator having a water supply inlet structure disposed at the top.

Vertical steam generators have a tube bundle located within a shell structure and surrounded by a jacket. An annular passageway is formed between the jacket and the barrel. Feed water entering the top of the barrel flows down the annular passage and rises through the tube bundle where it is heated by the primary fluid passing within the tubes. In some steam generators, feed water enters a feed water inlet ring located above the tube bundle. Early water inlet rings were designed to discharge the water supply through holes in the bottom of the ring. This can create a steam trap at the top of the ring that can cause water hammer due to bubble collapse as the sudden depressurization of the void occurs as cold water enters the void. The structure of such a water supply ring was modified to provide top discharge from a J-shaped nozzle. This allows steam to rise from the ring and also allows the favorable feature of directing the water supply towards the tubesheet in the annular passage between the jacket and the shell. This results in distribution of the water supply according to the desired ratio at the height of the water supply inlet ring. Examples of bottom discharge and J-shaped water rings are U.S. Pat. No. 4,037,569 and U.S. Pat. No. 3,991,720.
They can be found in the respective specifications.

In either water ring configuration, stratification or stratification of the flow in the water pipes and nozzles can occur due to thermal and hydraulic mechanisms. The thermal scheme includes heating the feed water along the feed water ring. Once the feed water enters the steam generator, it receives heat via thermal conduction in the ring walls. After that, J.
In shaped water rings, buoyancy comes into play as it allows the water supply to exit through some J-shaped pipes while hot water enters through other J-shaped pipes. Hydraulic mechanisms are the main cause of flow stratification in water rings with bottom hole discharge. In this case, the feed water enters the steam generator and is discharged through some bottom holes, while hot water enters the ring through other bottom holes.

It is therefore an object of the present invention to provide a steam generator in which water hammer phenomena, which often lead to structural damage, can be avoided by improving the flow of feed water by including steam voids.

To achieve the above-mentioned objects, the present invention comprises a cylindrical barrel, a plurality of U-shaped tubes disposed within the barrel and forming a tube bundle, and extending across the barrel and extending from the ends of the U-shaped tubes. a tube sheet having a plurality of apertures for receiving the tube bundle; a sheathing surrounding the tube bundle and forming an annular passageway away from and proximate the barrel; an inlet tube having a substantially horizontal section; and a discharge nozzle provided at the end of the inlet tube for supplying the secondary fluid to the shell above the tube bundle; In a steam generator that uses a primary fluid to vaporize a secondary fluid, the inlet pipe has a horizontal portion extending through the shell such that the discharge nozzle rises above the horizontal portion of the inlet pipe. The tube bundle is extended and raised up within the shell, and above the tube bundle, there is a
A waterway for receiving secondary fluid from the discharge nozzle is disposed extending diametrically across the barrel, the waterway having an open upper end in fluid communication with the annular passageway beyond the discharge nozzle. It is characterized in that the inlet pipe is located above and stands up within this waterway.

As described above, in the steam generator according to the present invention, (1) a water channel having an open upper end is provided, and (2) the water channel extends diametrically across the body of the steam generator. (3) the inlet pipe has a discharge nozzle raised within the channel as described above; and (4) the open upper end of the channel extends beyond the discharge nozzle. Since the pipe also extends upwards, the flow of steam voids and feed water is improved and water hammer is avoided both in the channel and in the inlet pipe.

The present invention will be explained clearly and in detail below with reference to the drawings showing preferred embodiments.

Referring to the drawings, FIG. 1 shows a steam generator 10 which is used to transfer heat from a primary fluid to provide the heating surface necessary to vaporize or boil a secondary fluid. A plurality of U-shaped tubes forming a tube bundle 12 are used. Evaporation generator 10
a container having a vertically oriented cylindrical body 14;
It consists of an enclosure or flanged dish-shaped head 16 surrounding the upper end and a spherical water chamber 18 surrounding the lower end. The lower body 14 has a smaller diameter than the upper head 16, and a frusto-conical intermediate member 20 connects the upper and lower parts. The tubesheet 22 is integrally formed with the water chamber 18 and has a plurality of holes 24 disposed therein for receiving the ends of the U-shaped tubes. A separating plate 26 is disposed centrally within the water chamber 18 and divides the water chamber into two compartments 28 and 30 which serve as tube bundle headers. Compartment 30 is a primary fluid inlet compartment and has a primary fluid inlet nozzle 32 in fluid communication therewith. Compartment 28 is a primary fluid outlet compartment and has a primary fluid outlet nozzle 34 in fluid communication therewith.

Therefore, the primary fluid entering compartment 30 is directed to tube bundle 12
and exit through the outlet nozzle 34.

The tube bundle 12 is surrounded by a jacket 36 which defines an annular passage 38 with the body 14 . The upper end of the covering body 36 is covered by a lower deck plate 40.
0 includes a plurality of openings 42 in fluid communication with a plurality of risers 44 . Swirl vanes 46 are disposed within the riser to impart rotation to the steam flowing through the riser and centrifugally remove some of the moisture contained in the steam as it flows through the centrifuge. After flowing through the centrifuge, the dish head 1
Secondary fluid steam outlet nozzle 5 provided in the center of 6
Before reaching zero, the vapor passes through a corrugated plate separator 48.

The steam generator feedwater inlet structure includes a feedwater inlet pipe 52 having a substantially horizontal section 54 and a discharge nozzle 56 raised above it. A conduit 58 located above the steam generator tube bundle and proximate lower deck plate 40 receives secondary fluid from discharge nozzle 56 and has an open upper end in fluid communication with annular passage 38. .

The water supply supplied via the water supply inlet pipe 52 is passed through the raised discharge nozzle 56 to the open water channel 58.
Go inside. In the open channel 58, the feedwater falls over the top of the open channel, mixes with moisture separated from the steam, and is recycled. The mixture then flows down into the annular passage 38.

FIG. 2 is a plan view of a water supply inlet structure constructed in accordance with one embodiment of the present invention. In this embodiment, a porous partition plate 60 is added to the open channel 58 to minimize the increase in secondary liquid level that could result from the generally horizontal discharge of the discharge nozzle 56. . This drawing also shows the waterway 58
is shown extending radially across the steam generator shell. 3 is a sectional view taken along line - of the water supply inlet structure of FIG. 2; FIG. In this figure, a porous partition plate 60 has a plurality of openings 62
appears to contain. In addition, the water supply inlet pipe 52
includes a substantially vertical portion 64 for arranging the water supply discharge nozzle 56 as required above the substantially horizontal portion 54 of the water supply inlet pipe. The level of secondary fluid 66 is typically maintained above the open top of conduit 58 .

By locating the feedwater discharge nozzle at some height above the horizontal section of the feedwater inlet pipe, the discharge nozzle and the feedwater inlet pipe are exposed to cold inlet water before the water is discharged into the steam generator. It should be satisfied. Therefore, only stratified water distribution is possible due to the rapid heating of the inlet water prior to its discharge from the feedwater inlet pipe into the steam generator. The open channel construction eliminates steam traps so that any steam that may collect or form within the water inlet structure can travel upwards within the natural circulation direction. You can see that it is. To allow the generated steam to travel upward by natural convection, away from the cold feed water, the feed water inlet structure allows steam to escape vertically upward through its length.

Using the present invention, thermal shock of steam generator components can be prevented by providing a physical shield that prohibits incoming feed water from contacting other components of the steam generator. Proper selection of the thermal shield will keep the incoming water supply away from the shell and other components long enough for it to be heated or mixed with the hot recirculating fluid. The open diameter channels used in this invention are of simpler construction than J-tube water rings. Furthermore, the water supply system can be integrated with the primary separator package and accommodate an increased number of risers.

The open-diameter water channel has a configuration that prevents trapping of vapor space, thereby preventing water hammer due to bubble collapse. The completely open top allows any steam voids that sink or form within the waterway to rise away from the waterway by natural circulation. A raised inlet nozzle requires the inlet flow to fill the inlet pipe and exhaust nozzle before any inlet water is discharged to the steam generator. Therefore, it is essentially impossible for small flows to stratify within the water supply pipe because the stratified layer must rise as the riser of the water supply inlet pipe is filled with cold water. Another mechanism for stratification, heat transfer to the water within the inlet tube, is reduced by the fact that the inlet tube stands up vertically and reaches its full height with a minimum heat transfer area exposed to the hot ambient environment. Thermal shock is minimized by directing the incoming feedwater directly into the open channel, where it mixes with recirculated water and is heated as it flows over the top of the channel. The water supply then proceeds circumferentially and radially before contacting the upper body.

[Brief explanation of drawings]

Fig. 1 is a partially transparent perspective view showing a vertical steam generator according to an embodiment of the present invention, Fig. 2 is a plan view showing a water supply inlet structure according to an embodiment of the invention, and Fig. 3 is a line taken along the - line in Fig. 2. FIG. DESCRIPTION OF SYMBOLS 10... Steam generator (cylindrical body), 12... Tube bundle, 22... Tube sheet, 36... Covering body, 38... Annular passage, 52... Inlet pipe, 54... Horizontal portion, 5
6... Discharge nozzle (discharge nozzle), 58... Water channel.

Claims (1)

[Claims] 1 a cylindrical barrel, a plurality of U-shaped tubes disposed within the barrel and forming a tube bundle, extending across the barrel;
a tubesheet having a plurality of openings for receiving ends of the U-shaped tubes; a cladding surrounding the tube bundle and forming an annular passageway away from and proximate the barrel; and connected to the barrel; an inlet tube for introducing a secondary fluid into the shell and having a substantially horizontal section; an inlet tube provided at the end of the inlet tube for supplying the secondary fluid to the shell above the tube bundle; In a steam generator that uses a primary fluid to vaporize a secondary fluid, the inlet pipe includes a discharge nozzle and a discharge nozzle.
The horizontal portion extends through the shell and is raised within the shell such that the discharge nozzle rises above the horizontal portion of the inlet tube, and above the tube bundle is the discharge nozzle. A waterway for receiving secondary fluid from the nozzle is disposed extending diametrically across the barrel, the waterway having an open upper end in fluid communication with the annular passageway above the discharge nozzle. A steam generator characterized in that the inlet pipe is raised within the waterway.